We’ve stored a huge chunk of what we “know” in people around us for eons. But we rarely recognize this because, well, we prefer our false self-image as isolated, Cartesian brains. Novelists in particular love to rhapsodize about the glory of the solitary mind; this is natural, because their job requires them to sit in a room by themselves for years on end. But for most of the rest of us, we think and remember socially. We’re dumber and less cognitively nimble if we're not around other people—and, now, other machines.
Aikin and Talisse:
In short, we argue in pursuit of truth. The epistemic conception is concerned with rationally engaging others. It is, after all, through such engagement that we come to see more fully what reasons and evidence there are, and thus we come to occupy a better vantage point from which to evaluate our options, including the beliefs we already hold. In this way, the epistemic conception sees argument as a critical activity aimed at the evaluation of views. But note that argument then is equally a self-critical activity, a process by which we can criticize our own views. The thought is that by engaging together in pursuit of truth, we can help each other to refine our ideas, even in the face of persistent disagreement.
The epistemic view accordingly proposes its own conception of respect. The rhetorical theory takes respect to consist in the willingness to reason from another's premises. The epistemic conception locates respect in seeing others as partners in the common pursuit of believing what's right by believing what the best available reasons and evidence favor. The rhetorical view has it that I respect you when I take you as you are -- with the beliefs you already have -- and attempt to rationally compel you to move in my direction. The epistemic view holds that I respect you when I regard you as a companion in a common struggle for truth, and thus a fellow source of reasons, ideas, evidence, and objections.
Without conversation and challenge, philosophy very quickly lapses in to the dead dogma that Mill feared. But that does not mean that every viewpoint is equally valuable, or that we should accept that each person finds their own truth. Every great philosopher has been driven by an attempt to get beyond appearances and to say something important about how things really are. Philosophy is a subject that weighs positions, not just airs them. Conversation without critical judgment becomes mere chatter and airing of different opinions — as William Empson wrote in his poem ‘Let It Go’ (1949):
The contradictions cover such a range.
The talk would talk and go so far aslant.
You don't want madhouse and the whole thing there.
However, it was John Stuart Mill who crystallised the importance of having your ideas challenged through engagement with others who disagree with you. In the second chapter of On Liberty (1859), he argued for the immense value of dissenting voices. It is the dissenters who force us to think, who challenge received opinion, who nudge us away from dead dogma to beliefs that have survived critical challenge, the best that we can hope for. Dissenters are of great value even when they are largely or even totally mistaken in their beliefs. As he put it: ‘Both teachers and learners go to sleep at their post, as soon as there is no enemy in the field.’